Lighting systems are formed typically by interconnecting many light fixtures by a communications system and providing for operator control from a central controller. Such lighting systems may contain multiparameter light fixtures, which illustratively are light fixtures having two or more individually remotely adjustable parameters such as beam size, color, shape, angle, and other light characteristics. Multiparameter light fixtures are widely used in the lighting industry because they facilitate significant reductions in overall lighting system size and permit dynamic changes to the final lighting effect. Applications and events in which multiparameter light fixtures are used to great advantage include showrooms, television lighting, stage lighting, architectural lighting, live concerts, and theme parks. Illustrative multi-parameter light devices are described in the product brochure entitled “The High End Systems Product Line 2001” and are available from High End Systems, Inc. of Austin, Tex.
A variety of different types of multiparameter light fixtures are available. One type of advanced multiparameter light fixture which is referred to herein as an image projection lighting device (“IPLD”) uses a light valve to project images onto a stage or other projection surface. A light valve, which is also known as an image gate, is a device for example such as a digital micro-mirror (“DMD”) or a liquid crystal display (“LCD”) that forms the image that is projected. U.S. Pat. No. 6,057,958, issued May 2, 2000 to Hunt, incorporated herein by reference, discloses a pixel based gobo record control format for storing gobo images in the memory of a light fixture. The gobo images can be recalled and modified from commands sent by a control console. A pixel based gobo image is a gobo (or a projection pattern) created by a light valve like a video projection of sorts. U.S. Pat. No. 5,829,868, issued Nov. 3, 1998 to Hutton, incorporated by reference herein, discloses storing video frames as cues locally in a lamp, and supplying them as directed to the image gate to produce animated and real-time imaging. A single frame can also be manipulated through processing to produce multiple variations. Alternatively, a video communication link can be employed to supply continuous video from a remote source.
U.S. Pat. No. 5,828,485, issued Oct. 27, 1998 to Hewlett, incorporated herein by reference, discloses the use of a camera with a digital micro mirror equipped light fixture for the purpose of following the shape of the performer and illuminating the performer using a shape that adaptively follows the performer's image. A camera capturing the image preferably is located at the lamp illuminating the scene in order to avoid parallax. The image can be manually investigated at each lamp or downloaded to some central processor for this purpose.
United States patent application titled “METHOD, APPARATUS AND SYSTEM FOR IMAGE PROJECTION LIGHTING”, inventor Richard S. Belliveau, publication no. 20020093296, Ser. No. 10/090926, filed on Mar. 4, 2002, incorporated by reference herein, describes prior art IPLDs with cameras and communication systems that allow camera content, such as in the form of digital data, to be transferred between IPLDs.
IPLDs of the prior art use light from the projection lamp that is sent though a light valve and focused by an output lens to project images on a stage. The light cast upon the stage by the IPLD is then imaged by the camera. U.S. Pat. No. 6,219,093 to Perry titled “Method and device for creating the facsimile of an image”, incorporated herein by reference describes a camera that may be an infrared camera for use with a described lighting device that uses liquid crystal light valves to project an image. “Accordingly the camera and light are mounted together for articulation about x, y, and z axes as is illustrated in FIG. 1” (Perry, U.S. Pat. No. 6,219,093, col. 4, line 59).
The prior art patent to Perry, U.S. Pat. No. 6,219,093 makes use of a camera to distinguish objects in the camera's field from other objects. The distinguished object as imaged by the camera is then illuminated by the projected light passing through the light valves so as to only illuminate the distinguished object. The objects may be provided with an infrared emitter or reflector which interacts with a receiver or camera. Perry relies on the light produced from the projection lamp and the light valves to provide the illumination to the scene where the camera images or separate emitters or reflectors are provided with the objects on the stage. The Perry prior art patent describes its invention as a camera/light unit.
United States patent application titled “METHOD AND APPARTUS FOR CONTROLLING IMAGES WITH IMAGE PROJECTION LIGHTING DEVICES”, inventor Richard S. Belliveau, Ser. No. 10/206,162, filed on Jul. 26, 2002, incorporated by reference herein, describes control systems for IPLDs and IPLDs with cameras and more specifically the control of images in a lighting system that includes multiparameter lights having an image projection lighting parameter.
United States patent application titled “IMAGE PROJECTION LIGHTING DEVICES WITH VISIBLE AND INFRARED IMAGING”, inventor Richard S. Belliveau, Ser. No. 10/290,660 filed on Nov. 8, 2002, incorporated by reference herein, describes IPLDs that contain cameras that can capture both visible and infrared images.
IPLDs may project images such as video images or still images or they may project only light with no image. The projection of images by IPLDs is useful in creating a visual scene on the projection surface that can create an animation or a representation of objects. The projection of only light with no image on the projection surface such as white light or colored light is useful in providing illumination of the projection surface. Most often when illumination of the projection surface without images is required the intensity of the illumination should be uniform across the projection surface.
U.S. Pat. No. 6,188,933 to Hewlett discloses “Another possible DMD effect is the simulation of a beam field distribution or profile, e.g., a cosine shaped profile for the spotlight. The inventors recognized that spotlights are often overlapped with other spotlights at their edges. The area of overlap can cause a bright spot at those edges. The DMD is used to form a spotlight with edge portions that have intensities that are lower than the intensity in the center of the beam. The rate of intensity drop off is preferably a cosine function. In this way, when the two edge portions of two spotlights are placed one over the other, the overlap does not appear to be overly bright. However, such variable profiles will not be desired in all situations. A variable brightness profile will be desired in situations where multiple beams will be overlapping at their edges. However, other effects, such as illuminating a gobo, will be better illuminated using flat intensity profiles.” Hewlett describes varying the field distribution of the entire projected light. It will be seen in the following disclosure that the invention provides a better method of providing a uniform light on a projection surface using multiple IPLDs.
When multiple IPLDs of the prior art project light onto a projection surface such as a stage often the projected light from one IPLD overlaps another. The overlapped areas visibly displays an intensity increase because the projected light in the overlapped areas can be effectively double that compared to the non-overlapping areas. In some cases the overlapped areas may involve three or more IPLDs causing the overlapped areas to look distractingly brilliant compared to the nonoverlapped areas. In many applications using multiple IPLDs to light a projection surface it is highly desirable to have uniform intensity across the projection surface.
When IPLDs project images such as video images it is often desirable for the IPLD to be able to project light with the same intensity across the projection field. If the projection field is not uniform such as with more light intensity in the center of the projection field than at the edges, the projected image may have a visual hot spot in the center. This visual hotspot in the center of an IPLD's projected image can be distracting and undesirable when viewed.
When multiple IPLDs or other lighting devices are used to provide lighting for large area projection surfaces such as a stage floor in the prior art, the projection field may be adjusted to provide more light intensity in the center of the projection field than in the edges. The thinking being that where the IPLDs or other lighting devices overlap the intensity at the edges of each projection field is less therefore the overlapped areas will not be so intense compared to the center. This prior art method only results in reducing the distraction caused by overlapped areas and if there is the overlapping of three IPLDs projection fields the problem with visible higher intensity at that point still persists.